RTX2070 is certainly a good choice for 1440p@60hz. RTX2060 is also enough for now, but maybe not as game demands rise. RTX2070 is a little overkill for 1080p, but you could always run with v-sync off and see how many FPS you get. When the frames are fast enough, tearing isn't all that bad.
If you can afford the more expensive card it should last longer before needing a replacement. That is something you have to decide on. Do you target an upgrade cycle or wait until there is something you want to run that you can't? Look for technological milestones and buy into that? RTX, next process node shrink?
Many people ride the mid-range cards. Never spending too much, but updating a little more often.
I like to buy a larger card and keep it until it is nearly worthless. We both end up spending about the same, but the bigger cards let me run high end stuff at launch without compromising. Now my current system I am always compromising since my card can't deliver 144FPS 1440p on the latest games, but everything is still above 60FPS easily. And I play many older titles, or titles with less demands, and there I get the benefit of my monitor.